Load equalization method for new connections in a wireless environment supporting shared access for multiple terminals in a QoS controller manner

ABSTRACT

The present invention relates to a method of smoothing load over multiple bearers in a given spot-beam for a TDMA wireless personal communication system, offering packet data communication services to individual user terminals in shared mode. The present invention also relates to a method for the smoothing of load over multiple bearers in a given sport beam for a TDMA wireless personal communication system which allows maintenance of minimum service levels as a guarantee to individual connections as well as optimizing distribution of users to all available radio channels. The method of the invention is also enabled to distinguish between whether a particular bearer is QoS-blocked or demand-blocked. The method of the invention uses either a loose smoothing algorithm or a tight smoothing algorithm for the load control operation based on the above dispensation.

The present invention relates to a method of smoothing load overmultiple bearers in a given spot-beam for a TDMA wireless personalcommunication system, offering packet data communication services toindividual user terminals in shared mode. The present invention alsorelates to a method for the smoothing of load over multiple bearers in agiven sport beam for a TDMA wireless personal communication system whichallows maintenance of minimum service levels as a guarantee toindividual connections as well as optimizing distribution of users toall available radio channels. The method of the invention is alsoenabled to distinguish between whether a particular bearer isQoS-blocked or demand-blocked. The method of the invention uses either aloose smoothing algorithm or a tight smoothing algorithm for the loadcontrol operation based on the above dispensation.

The algorithm used in the method of the invention has the followingoperating environment and implementation

-   -   The method is concerned with re-deploying connections over        available in-use radio channels in the single cell of a given        cellular environment, thus offering balanced performance on all        radio-channels. The redeployment is considered a relatively        inexpensive procedure and is carried out by sending a message to        the terminal to retune its receivers to a new radio-channel.    -   Each user can be mapped to a given QoS level, which is known to        the algorithm. The QoS level can be mapped to the minimum amount        of bandwidth that has to be given to the user, when the user has        data to send, for the QoS guarantee to be met. The definition of        QoS is such that, if the actual bandwidth offered to the user is        greater than the minimum level (measured on a frame by frame        basis), the actual QoS seen by the user is better than the        guaranteed QoS level.    -   The existence of a scheduling algorithm is assumed, which        decides on the fine-grained allocation of radio-resources to        individual connections. The scheduling algorithm operates on the        same QoS levels as described above.    -   For each user, a measured demand and an anticipated demand is        assumed. The measured demand is the actual requirement for        resources for that user, and the anticipated demand is computed        as I_(g)        T_(g)=total service requested in current backlog period in        bytes;        D_(g)=duration of current backlog period;        I_(g)=T_(g)/D_(g);        if (I_(g)>offered b/w)    -   addl. Pot. Demand=I_(g)−offered b/w;        else addl. Potential demand=0,    -   The method calls for the computation of surplus capacity for        each radio channel. The surplus capacity is the bandwidth        available after all connections have been serviced at the        minimal QoS level    -   The method calls for the computation of the total potential        demand for each active user terminal in the cell.    -   The method calls for the computation of the offered bandwidth        for each terminal by measuring the average bandwidth given to        the terminal during its latest backlog period.    -   The method calls for the computation of the total deficit demand        for each user terminal by computing the difference between the        total demand and the offered bandwidth. The total deficit        bandwidth for a given radio-channel is measured by summing the        deficit bandwidths for all terminals using that radio-channel.    -   For the entire cell, we compute the total deficit demand and the        total surplus capacity. If the total deficit demand is greater        than the total surplus capacity, we execute the tight smoothing        algorithm as follows;        -   for each bearer, the ratio between the total estimated            deficit of all the mobile terminals using that bearer and            the surplus on that bearer is computed. This ratio is called            the bearer adequacy ratio (BAR).        -   For the entire spot-beam, there is a configured threshold            adequacy ratio.        -   all the bearers whose current adequacy ratio is less than            the threshold in increasing order of BAR are listed. This is            the list of bearers which have additional capacity            available, it is called the T-table        -   all the bearers whose current adequacy ratio is greater than            the threshold in decreasing order of BAR is listed. This is            the list of bearers which need to create additional            capacity, and is called the D-table.        -   a pair comprising of one member from the T-table and one            from the D-table as described above are identified. The pair            of bearers are chosen such that there is one connection in            the bearer from the D-table, which may be returned to the            bearer in the T-table. The conditions for this to happen            will include (a) whether the absolute utilization of the            connection is less than the absolute surplus in the first            bearer (b) application specific or system specific            conditions.        -   To find the optimal pair, the first entries from the D-list            and T-list are taken to see if a pair can be formed. If the            1^(st) member from either or both lists is not acceptable,            the method continues down the to the second entry and so            forth.        -   A retune of the chosen connection from the 2^(nd) member of            the pair to the 1^(st) member in the pair is executed. This            pair is then marked as ineligible for further transfers in            this cycle and the method continues on with the rest of the            members in the list.    -   If the cell is in ‘tight smoothing’, the higher layer resource        manager is informed that further resources are required in this        cell. It is up to the higher layer resource manager as to        whether it allots fresh resources, or whether it imposes        congestion control features in this cell.    -   For the entire cell, the total deficit demand and the total        surplus capacity is computed. If the total deficit demand is        less than the total surplus capacity, the loose smoothing        algorithm is executed as follows.        -   In the entire cell, the User connections which have deficit            demand are listed in increasing order of deficit, the U-list        -   In the entire cell, the bearers in surplus capacity are            listed in increasing order of surplus, the B-list.        -   the first entry in the U-list of connections are taken and            the 1^(st) entry in the bearer see whether (a) the surplus            on its current bearer is less than the surplus on the            selected bearer and (b) it can be returned to the selected            bearer. If so, a retune is done and the bearer struck off            the B-list, as well as the connection off the U-list. If            not, the method continues to search in the B-list to find a            suitable bearer. This is repeated for all entries in the            U-list.

The above description should not be construed as limiting in any manner.Work is still underway in completing the invention. It will be evidentthat modifications and variations are possible without departing fromthe scope and spirit of the invention.

1. A method of smoothing load over multiple bearers in a given spot-beamfor a TDMA wireless personal communication system, offering packet datacommunication services to individual user terminals in shared mode, themethod comprising applying an operating algorithm wherein: (a)connections are re-deployed over available in-use radio channels in thesingle cell of a given cellular environment, thus offering balancedperformance on all radio-channels; the re-deployment being effected bysending a message to each terminal to retune its receivers to a newradio-channel; (b) mapping each user to a given QoS level, which isknown to the algorithm. (c) assuming the existence of a schedulingalgorithm which decides on the fine-grained allocation ofradio-resources to individual connections; (d) assuming a measureddemand and an anticipated demand for each user; (e) computing a surpluscapacity for each radio channel, the surplus capacity being thebandwidth available after all connections have been serviced at theminimal QoS level; (f) computing total potential demand for each activeuser terminal in the cell; (g) computing offered bandwidth for eachterminal by measuring the average bandwidth given to the terminal duringits latest backlog period; (h) computing total deficit demand for eachuser terminal by computing the difference between the total demand andthe offered bandwidth; (i) computing total deficit demand and the totalsurplus capacity for the whole cell; (j) if the total deficit demand isgreater than the total surplus capacity, executing a tight smoothingalgorithm; or if the total deficit demand is less than the total surpluscapacity, executing a loose smoothing algorithm; (k) if the cell is in‘tight smoothing’, informing a higher layer resource manager thatfurther resources are required in the cell.
 2. A method as claimed inclaim 1 wherein the QoS level is mapped to the minimum amount ofbandwidth that has to be given to a user, when the user has data tosend, for the QoS guarantee to be met.
 3. A method as claimed in claim 1wherein the QoS is defined such that if actual bandwidth offered to theuser is greater than a minimum level measured on a frame by frame basis,the actual QoS seen by the user is better than the guaranteed QoS level.4. A method as claimed in claim 1 wherein the scheduling algorithmoperates on the same QoS levels as the operating algorithm.
 5. A methodas claimed in claim 1 wherein the measured demand is the actualrequirement for resources for that user, and the anticipated demand iscomputed as I_(g).
 6. A method as claimed in claim 5 wherein the totalservice requested in current backlog period in bytes is T_(g), andwherein D_(g)=duration of current backlog period and whereinI_(g)=T_(g)/D_(g) if (I_(g)>offered b/w) and wherein addl. Pot.Demand=I_(g)−offered b/w, else addl. Potential demand=0.
 7. A method asclaimed in claim 1 wherein the total deficit bandwidth for a givenradio-channel is measured by summing the deficit bandwidths for allterminals using that radio-channel.
 8. A method as claimed in claim 1wherein the tight smoothing algorithm is executed by (a) computing foreach bearer a bearer adequacy ratio (BAR), the ratio being between thetotal estimated deficit of all the mobile terminals using that bearerand the surplus on that bearer; (b) maintaining for the entirespot-beam, a configured threshold adequacy ratio; (c) preparing a list(hereinafter called T-table) comprising all the bearers whose currentadequacy ratio is less than the threshold in increasing order of BAR arelisted; (d) preparing a list (hereinafter termed D-table) comprising allthe bearers whose current adequacy ratio is greater than the thresholdin decreasing order of BAR is listed, the bearers being bearers who needto create additional capacity; (e) identifying a pair comprising of onemember from the T-table and one from the D-table, the pair of bearersbeing chosen such that there is one connection in the bearer from theD-table, which is returnable to the bearer in the T-table. (f) findingan optimal pair by taking a first entry from the D-table and T-table andif the first member from either or both tables is not acceptable,continuing down the lists to the second entry and so one; (g) executinga retune of the chosen connection from the second member of the pair tothe first member in the pair and marking the pair as ineligible forfurther transfers in this cycle and continuing the step with othermembers in the list; (h) informing the higher layer resource manager ifthe cell is in ‘tight smoothing’, that further resources are required inthis cell
 9. A method as claimed in claim 8 wherein the higher layerresource manager determines on whether fresh resources should beallotted or whether congestion control features should be imposed inthis cell.
 10. A method as claimed in claim 1 wherein the loosesmoothing algorithm is executed by: (a) listing in the entire cell, theuser connections which have deficit demand in increasing order ofdeficit (hereinafter called the U-list); (b) listing in the entire cell,the bearers in surplus capacity in increasing order of surplus,(hereinafter termed as the B-list); (c) taking the first entry in theU-List of connections, the 1^(st) entry in the bearer seeing whether (a)the surplus on its current bearer is less than the surplus on theselected bearer and (b) if the surplus on its current bearer can bereturned to the selected bearer, and then retuning being carried out andthe bearer struck off the B-list, as well as the connection off theU-list, and if not, the method continuing to search in the B-list tofind a suitable bearer, this step being repeated for all entries in theU-list.
 11. A method as claimed in claim 10 wherein execution of thetight smoothing algorithm is dependent (a) whether the absoluteutilization of the connection is less than the absolute surplus in thefirst bearer (b) application specific or system specific conditions.